Workpiece defect severity classifier with timing circuit to divide workpiece into equal inspection quadrants

ABSTRACT

A workpiece 18 classifying and marking system 10 is disclosed. The system includes a probe 12 for generating signals in response to the detection of defects along the workpiece length as that workpiece rotates and traverses past the probe 12. Circuitry coupled to the test head analyzes defects according to severity and classifies the workpiece as either &#34;good&#34;, &#34;salvageable&#34;, or &#34;scrap&#34;. The circuitry also causes a marker 14 to affix a flaw indicating mark to the workpiece at the flaw location. 
     The circuitry includes a flaw detection circuit 60, a defect classifying circuit 72, a timing control circuit 70, and a marker delay circuit 74. The timing control 70 transmits timing signals of different frequency to the defect classifying 72 and marker control 74 circuits and coordinates their operation. The defect classify circuit 72 divides the workpiece into quadrants and can sense the length of any flaws in each quadrant as the workpiece passes the probe 12. The detection of a flaw causes the timing control circuit to resynchronize itself by centering the flaw within a workpiece quadrant thereby preventing the flaw from &#34;wandering&#34; out of the quadrant. The circuitry is controllable by the user to change workpiece classification as a function of the use to which the workpiece is to be put.

This is a continuation of application Ser. No. 127,579 filed Mar. 6,1980, now U.S. Pat. No. 4,365,198.

TECHNICAL FIELD

This invention relates to flaw inspection in work pieces and morespecifically to circuitry for controlling marking and classification offlaws in steel billets or bars.

BACKGROUND ART

Work piece flaw detection and classification systems are known. TheRepublic Steel Corporation has developed a number of innovative flawdetecting systems and a number of patents have issued describing thesesystems.

One of the earlier Republic Steel flaw detecting patents is U.S. Pat.No. 2,660,704 to Harmon. That patent discloses a test device forlocating flaws such as cracks, seams, breaks, and the like in a steelworkpiece by measurements conducted at the surface of the workpiece. Theapparatus disclosed in the '704 patent includes a search unit adapted tobe positioned upon or adjacent a workpiece and for subjecting theworkpiece to a periodically varying electro-magnetic field produced by acoil carried in the search unit. Suitable control and flaw indicationcircuitry is coupled to the search unit to convert signal variationsproduced by movement of the search unit about the workpiececircumference into an indication as to the relative characteristics ofthe various portions of the bar. U.S. Pat. Nos. 2,914,726 and 2,832,040disclose improvements and refinements in the technique disclosed in the'704 patent.

Two more recent Republic Steel patents disclose control circuitry andapparatus for utilizing the detecting principle disclosed in the '704patent to classify and mark the position of defects in steel bars asthey are tested. These two patents are U.S. Pat. Nos. 3,108,230 to Juddet al and 3,263,809 to Mandula et al. Both patents are used inconjunction with a test probe which is moved relative to a steel bar andcoupled to energization circuitry for generating electromagnetic signalswithin the bar.

According to the '809 patent, the defect information obtained by theprobe or test head is acted upon by a detection circuit which producesan output voltage pulse in response to the presence of a defect. Thepulse amplitude is related to the depth of the defect and is introducedto a classifier circuit having two channels. One channel generates atrigger signal each time a relatively deep defect is sensed and a secondchannel generates a trigger pulse each time either a shallow or a deepdefect has been sensed. These trigger pulses are introduced into ananalyzer section which counts the number of shallow and deep defecttrigger pulses for a given area of the workpiece, and from thisinformation determines the severity of the combinations of defects. Theanalyzer section then classifies the workpiece or bar according to thecombined severity as either good, salvage, or scrap.

As the name suggests, "good" workpieces are those which have no defects,or defects which are not objectionable since they do not impair theutility of the product for its intended purpose. Workpieces classifiedas "salvage" have defects deep enough to be objectionable but not toosevere to preclude repair. A "scrap" workpiece is one in which thedefects are so deep and so long that it is not possible to salvage theworkpiece.

The '230 patent discloses defect marking apparatus which marks thelocation of the defects on the workpiece. The marks made are permanentand easily visible even though the workpiece may be subject to abrasivehandling. The '230 patent discloses a rotating cutter of carbide orother material which is movable to engage the workpiece and cutimpressions therein at defect locations. An actuator is adapted to movethe cutter onto the workpiece for the duration of an energizing pulse.Actuation is coordinated with defect detection equipment constructed,for example, in accordance with the earlier Harmon patent. The detectionequipment and workpiece are relatively rotatable such that the detectionequipment describes a helical path around a longitudinally movingworkpiece. The control circuit is connected to both the detectionequipment and to the actuator on the defect marking equipment and causesan energizing signal to activate the actuator to effect appropriatedefect marking.

Since the cutter or marking system and the defect detection equipmentcannot be at the same physical location, the marker is placed behind or"downstream" of the detection equipment. Both are preferably placed on alongitudinal line along the bar. The longitudinal space between themarker and the detection equipment is chosen to equal the distance oftravel per revolution of workpiece movement. Upon receipt of a defectsignal from the detection equipment, the control circuit coupled to themarker system delays sending an energization signal for a period of timeequal to one bar revolution. Since forward bar travel per revolution isequal to the spacing between the detection equipment and the marker, theenergization signal causes the mark to be applied to the bar at thelocation of the detected defect.

The concepts embodied in the Mandula et al and Judd et al patents enablebars to be marked and classified in a unified system which has proven tobe very effective. The control circuitry utilized, however, forcoordinating bar marking and classification is an analog electroniccircuit which is not always sensitive to closely spaced multipledefects. The prior classification and marking system can only classifyseams or cracks once every revolution of a bar or workpiece. If aplurality of deep seams exist about the circumference of the bar, theMandula et al system analyzes only the first such defect and ignoressubsequently sensed defects. This lack of sensitivity in defect sensingcan result in errors in bar classification. If a short deep defect isfirst sensed along the path of workpiece travel, an accompanying longdeep defect may not be properly measured and therefore a workpiececlassified as good may in reality be either a salvage or scrap bar.

The prior art classification and marking system includes a plurality ofseparate analog timing circuits for controlling and coordinatingclassification and marking. Both the deep and shallow flaw measuringchannels in the classification circuit each has its own timing mechanismwhich resets the classification circuitry in its associated channelafter each bar revolution. In addition to these two timing circuits athird timing circuit is required to delay the marking of flaw positionon the workpiece. Typically, more than one marker is positioned alongthe workpiece and these multiple markers each require a separate timer.As bars of different physical dimensions are examined, each of themultiple timers must be adjusted by the system operator.

In the prior art classifying process an attempt was made toresynchronize the multiple timing control circuits in response to thepresence of flaws along the bar. The resynchronization circuitry wasanalog electronics, however, and was subject to drift in operatingcharacteristics with temperature. Synchronization between the timingcircuitry and bar rotation could be lost with possible inaccurate barclassification as well as inaccurate marking of flaw location.

Thus, although the prior art techniques for marking and classifyingsteel bars were effective, they exhibited shortcomings. In particular,the resynchronization and timing procedures utilized in the prior artclassifying system were somewhat ineffective. In addition to thesedisadvantages, the prior art analog circuitry was weighty, consumed amoderate amount of power and was subject to drift in operatingcharacteristics with temperature.

DISCLOSURE OF INVENTION

The present invention overcomes disadvantages noted with regard to theprior art by using a single timing circuit to synchronize theclassification and marking of defects along the length of a workpiece.With a single timing circuit only a single adjustment need be made forworkpieces of different diameters.

The invention includes a detector and detector circuitry for sensingdefects in a workpiece as the workpiece moves past a detector and forgenerating an output having a level related to the severity of adetected defect. The detector circuitry is coupled to a defectclassifying circuit which classifies the workpiece according to defectseverity. The defect detector circuitry is also coupled to workpiecemarking control circuitry for receiving defect signals and causing theposition of the defects to be marked on the workpiece. A single timingcircuit coupled to both the defect classifying circuit and the workpiecemarking circuit controls the operation of those circuits.

According to a preferred embodiment of the invention, the defectclassifying and marking circuits each include a storage circuit forstoring defect signals received from the detector. In the markingcircuit, the storage circuit provides a convenient technique fordelaying activation of a marker until the workpiece rotates one completerevolution after a defect is sensed. A signal from the detection circuitis stored in the marker circuit an appropriate time as dictated byclocking pulses from the timing circuit and then signals a markeractivation circuit. During this time the workpiece continues to rotateand traverse past the detector so that when the marker is activated thesensed defect is adjacent the marker.

The defect classification circuit storage circuit stores subsequent onesof defect signals from the detection circuit and provides a techniquefor classifying the defect according to length. The classifying storagecircuit includes a gating input for transmitting defect signals throughthe classifying storage circuit at a rate related to workpiece speed ofrotation and generated by the single timing circuit.

According to the preferred embodiment of the invention the classifyingcircuit storage portion comprises a serial shift register. Storagelocations in the shift register are sampled by logic circuitry todetermine the number of consecutive rotations of a bar being inspectedwhich produced signals indicating the presence of a particular defectand thereby determine the length of that defect. The timing controlcircuit clocks the shift register four times for every workpiecerevolution. If a defect signal is stored every fourth shift registerlocation for a significant portion of shift register memory it is knowna long seam has been sensed. By knowledge of the speed of workpiecetravel past the detector the length of this seam is known.

Clocking the shift register at a rate four times greater than workpiecerotation divides the workpiece into four quadrents for defectclassification. By dividing the workpiece into quadrents the circuitryprovides a degree of sensitivity unavailable in the prior art. Twodistinct defects occurring along the workpiece but in separate ones ofthe quadrants will each be analyzed and categorized according to lengthby the improved control circuitry.

The timing circuitry employed in the preferred embodiment of theinvention comprises a signal generator for generating two separateseries of pulses. Each of these series is coordinated with the workpiecerevolution. A first one of the series is coupled to the bar markingcontrol circuitry and serves as a gating signal to the marker storagecircuit discussed previously. The second of the two series of pulses isthe signal with a repetition frequency four times greater than theperiod of bar revolution for gating the classifying circuit serial shiftregister.

The timing circuit resynchronizes pulses in this second series upon thedetection of a workpiece defect. According to the preferred timingcircuit, the detection of a defect along the length of the bar causesthe next clocking pulse in the second series to occur one eighth barrevolution later in time. Once a defect is sensed, thisresynchronization centers the defect in the middle of a particularworkpiece quandrant as defined by the second series of pulses. Accordingto this scheme, variations in workpiece speed of rotation unlessdrastic, will not allow a particular flaw to "wander" out of itsparticular quandrant. The resulting resynchronization thereby results ina more accurate and more sensitive flaw classification circuit.

The preferred marker delay, classification and timing circuits aredigital. Digital circuitry is lighter, more reliable and consumes lesspower than the prior art analog control. It can be packaged in a smallerpackage and generally performs its control functions more reliably.

It should be apparent from the above that one object and aspect of thepresent invention is an increase in classifying circuit sensitivity andreliability to increase the accuracy of the classification technique. Asecond object of the invention is to provide a unified and simple timingcircuit to control both classification and marking. A third object andfeature is to resynchronize the classification circuitry each time adefect is sensed to insure that variations in the mechanical rotation ofthe bar do not introduce inaccuracies into the classification process.Other objects and features of the present invention will be understoodmore clearly when the present invention is considered in conjunctionwith the drawings and their description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of a workpiece inspection station.

FIG. 2 is a side elevation view of the inspection station as shown inFIG. 1.

FIG. 3 shows a general schematic of control circuitry for classifyingand marking the position of flaws on the workpiece.

FIGS. 4-7 are more detailed schematics of the control circuitry showngenerally in FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings, FIGS. 1 and 2 show a workpiece inspectionstation 10 where a flaw detection probe 12, marker 14 and drive roller16 are shown in proximity to a workpiece 18. The probe 12 is coupled toanalysis circuitry to be described which controls the marker 14 and alsocontrols classification of the workpiece under examination. The driveroller 16 provides relative movement between the probe 12 and theworkpiece 18.

As seen in FIG. 1, the roller 16 is supported by a float plate 20carried on both horizontal and vertical springs 22. A pair of hold downarms 24 with swiveled rollers 26 are carried by the float plate 20 abovethe drive roller 16. The hold down arms 24 include lever arm extensions28 which are pivoted by piston rods of two cylinders 30. The cylindersare actuated by a control valve 32 causing the hold down arms 24 to biasthe workpiece 18 in contact with the drive roller 16.

The roller 16 which supports the workpiece 18 is carried by a shaft 34which is rotatably journaled in a pillow block 36. The shaft 34 includesan extended shaft portion which extends beyond the pillow block fordriving connection to a suitable motor for providing rotation of theshaft and accompanying drive roller 16. The axes of rotation of theroller and accompanying shaft are set at an angle with respect to theline of travel of the workpiece. Rotation of the drive roller 16 causeslongitudinal movement of the workpiece 18 in a direction perpendicularto FIG. 1 as well as rotation about an axis co-incident with theworkpiece center.

Referring now to FIG. 2 an inspection and marking assembly support frame38 is positioned behind the drive roller 16 and mounted to the floatplate 20. The frame 38 supports a probe and marker carriage 40 which isslidably carried by the frame 38. The vertical position of the probe andmarker carriage 40 can be adjusted by rotating a hand crank 42 whichallows different size workpieces to be scanned. The probe 12 is carriedby a probe positioning shaft 44 which is attached to a piston rod of aprobe positioning cylinder 46. A solenoid actuated control valve (notshown) is pneumatically coupled to the cylinder 46 and controlsactuation of that cylinder to extend and retract its piston rod toposition the probe 12 against the workpiece 18.

The marker 14 is also carried by the inspection marking support frame38. The marker comprises a carbide cutter 48 which is fixed to a shaftof a motor 50. A spring (not shown) biases the cutter 48 in spacedrelation out of engagement with the workpiece 18. A cylinder carried bythe probe and marker carriage 40 has a piston rod connected to a shaftcollar at a point just above the cutter and causes the cutter 48 toengage the workpiece each time the cylinder is activated by a suitablecontrol signal such as a solenoid actuated air valve.

A gimbel assembly 52 connects the search probe 12 to the end of theprobe positioning shaft 44. The gimbel assembly 52 allows the searchprobe 12 to move universally at the end of the positioning shaft 44 asthe probe contacts the workpiece.

Although only one inspection station 10 has been shown, it should beappreciated that a plurality of such stations may be provided. Forexample, a number of inspection and marking assemblies may be spacedlongitudinally along the path of the workpiece travel so that eachinspection station inspects only a portion of the workpiece with allassemblies providing entire workpiece coverage.

The inspection station 10 shown in FIGS. 1 and 2 is an exemplaryinspection station. Other configurations and designs might be used inconjunction with the present invention to detect, classify and mark aworkpiece according to defect severity. Additional details of theexemplary inspection station 10 may be found in U.S. Pat. No. 3,263,809to Mandula et al which has been assigned to the assignee of the presentinvention. That patent is incorporated herein by reference.

The detection probe 12 is coupled electrically to circuitry forclassifying defects in the workpiece according to severity and length aswell as to circuitry for marking the location of these defects on theworkpiece A schematic of the circuitry comprising the present inventionis shown in FIG. 3. As seen in that Figure, the probe 12 is coupled to adetector circuit 60. The output from the detector circuit is coupled toa timing control circuit 70, a defect classifying circuit 72, and amarker delay circuit 74.

The input to the detector circuit comprises a signal related to thedepth of the defect or seam in the workpiece as detected by the probe12. Although only one detector circuit 60 is shown in FIG. 3, it shouldbe appreciated that a plurality of such detector circuits are requiredif workpiece inspection is apportioned among a plurality of inspectionstations.

The detector circuity 60 provides a classifying capability. It includesa threshold circuit which automatically classifies a defect as either ashallow or a severe defect and produces an output accordingly. Thedetector circuit 60 shown in FIG. 3 is known in the art and furtherdetails regarding such a detector circuit may be obtained by referenceto the '809 patent.

As seen in FIG. 3, one timing control circuit 70 is coupled to both thedefect classifying circuitry 72 and the marker delay circuitry 74. Theutilization of a single timing control circuit 70 to control delayoperations in the marking sequence as well as analysis operations in thedefect classifying circuitry is one desirable feature of the presentinvention. Unlike prior art systems, one timing control circuitcoordinates the marking and classification of the workpiece as thatworkpiece is scanned by the probe 12.

The defect classify circuit 72 includes a deep seam and shallow seamclassification channel. For this reason, the connection between thedetector circuit 60 and the defect classifying circuit 72 has been shownas two inputs 76, 78. One input 76 comprises an output from the detectorcircuit 60 from shallow seams and a second input 78 comprises detectorcircuit outputs from deep seams. In the exemplary embodiment of theinvention the shallow seam input 76 goes "high" when a shallow seam isdetected and both inputs 76, 78 go "high" when a deep seam is detected.

The defect classify circuit 72 is operative to classify both deep andshallow seams according to length. As will be described hereinafter thedefect classify circuit 72 includes manually controllable switches whichallow the user to choose a particular seam length as a criteria inclassifying the workpiece.

Each defect, whether shallow or deep, is marked by the carbide cutter 48under control of a marker control circuit 79. As noted above, thesequence of operations requires that a marker delay time period beintroduced between the detection of a flaw by the probe 12 and themarking of that same flaw by the cutter 48. The marker delay circuit 74achieves this function under the control of the timing control circuit70.

Once the entire workpiece has been analyzed for seam severity and lengtha workpiece classify circuit 80 indicates whether the particularworkpiece under study is a good, salvage, or scrap workpiece. Theworkpiece classify circuit 80 generates an output to a workpiece routingcontrol circuit 82 which causes each workpiece to be routed and storedaccording to its classification. The functioning of the defect classify72, timing control 70, marker delay 74, and workpiece classify 80circuits will be described in further detail with reference to FIGS.4-7. In those Figures the manufacturer's part numbers and pin numbersdesignations have been labeled on all integrated circuits to facilitatepractice of the present invention.

The preferred control circuitry shown in FIGS. 4-7 analyzes signals fromfour probes spaced along the length of the workpiece. Each probe has anassociated detection circuit 60 which generates an output signal foreach deep flaw sensed as well as each shallow flaw. Since there are fourprobes, there are four shallow 76a, b, c, d and four deep 78a, b, c, dseam inputs to the defect classify circuit 72.

As noted above, the defect classify circuit 72 comprises a deep seamchannel and a shallow seam channel. The shallow seam channel 110 isshown in FIG. 4 coupled to the four shallow seam inputs 76a, b, c, d.Circuitry identical to the circuitry shown in FIG. 4 receives the deepseam inputs and analyzes those inputs to categorize the deep seams in amanner identical to the shallow seam analysis to be described.

Each time any of the shallow seam inputs 76a, b, c, d goes high, it isan indication that an associated one of the four probes has detected ashallow seam along the workpiece length. As seen in FIG. 4, the fourshallow seam inputs are coupled to a Nor gate 112. Detection of ashallow seam causes this Nor gate to generate a low output which becomesa high level output after passage through a NAND gate 114. A NAND gateoutput 115 is coupled to a JK flip-flop 116. This flip-flop 116 changesstate in response to a high output from the NAND gate 114 unless it hasalready changed state in response to an earlier sensed shallow seam. Theflip-flop 116 is coupled to a first 150 of two shift 16 bit registers150, 152 via an output 117.

This flip-flop 116 is reset in response to an input 118 at pin 3 of theflip-flop from a one shot 120. The one shot in turn has an input labeledCLK from the timing control circuit 70. An input labeled CLK (not clock)from the timing control circuit 70 is a clocking input to the two shiftregisters 150, 152.

The 16 bit shift registers 150, 152 store shallow seam inputs 76a-d fromthe detection circuit 60 in response to the clock CLK and not clock CLKinputs. The appearance of a "high" shallow seam input (76 a-d) producesa "high" flip-flop output 117. The next low not clock CLK signal loadsthis "high" flip-flop output into the first shift register 150 at bitone. As the not clock CLK input goes low the clock input CLK goes high.After an eight microsecond delay introduced by the one shot 120 the CLKinput resets the flip-flop 116 thereby preparing it for the receipt ofother shallow seam inputs 76a-d.

The timing of the clock CLK and not clock CLK inputs from the timingcontrol circuit 70 to the one shot 120 is synchronized with rotation ofthe workpiece. As will become apparent four clock CLK pulses aregenerated for each rotation of the workpiece. Thus, four shallow seaminputs may be stored in the two shift registers per revolution of theworkpiece past the probe 12. Absence of a high bit in a particular shiftregister means a particular workpiece quadrant contains no shallow seamor flaw.

The timing control circuit is shown in FIG. 5. The clock output CLK tothe one shot 120 is shown at the bottom portion of that Figure. Thetiming control circuity 70 comprises an oscillator circuit 130, and afirst 132 and a second 134 frequency divider circuits. The firstfrequency divider 132 is adjustable by the user to generate an output136 such that the frequency of this output is related to the speed ofrotation of the workpiece. In the preferred embodiment of the invention,this output is chosen to have a repetition frequency 64 times greaterthan the period of rotation of the workpiece.

Adjustment of the frequency along the output 136 is achieved by settinga series of three thumbwheel switches coupled to the first frequencydivider 132. The setting of the thumbwheel switches is indicated bythree indicators 138-140 coupled to the thumbwheel switches. Thefrequency divider 132 receives the output from the oscillator 130 anddivides by the number appearing on the indicators 138-140. In thesetting shown in FIG. 5 the divider 132 divides the frequency of thesignal output by the oscillator 130 by 275. To achieve a divider output64 times greater than the speed of rotation of the workpiece, the userconsults a table which indicates the correct thumbwheel switch settingsfor each size workpiece the inspection station 10 is capable ofexamining and dials the appropriate number into the thumbwheel switches.

The output 136 from the first frequency divider 132 is first delayed bya two microsecond one shot 142 and then transmitted to the secondfrequency divider 134 via an input 143. In addition to being coupled tothe two microsecond one shot 142, the output 136 from the firstfrequency divider 132 is transmitted along an output 144 to the markerdelay circuit 74. It is this output 144 which determines the clockingrate of a serial shift register 146 within the marker delay controlcircuit 74. (see FIG. 7).

The second frequency divider 134 divides the signal from the firstfrequency divider 132 by 16. This division in frequency gives a clockingsignal CLK (as well as a not clock signal CLK) with a clock rate fourtimes greater than the frequency of rotation of the workpiece. From theabove, it should be apparent that the timing control circuit 70generates two outputs with differing clocking frequencies. The output144 to the marker delay circuit has a clock frequency 64 times greaterthan the frequency of rotation of the workpiece and serves as a clockingpulse for the marker delay circuitry to be described hereinafter. Theoutputs CLK and CLK to the defect classifying circuitry 72 have arepetition rate four times greater than the frequency of rotation of theworkpiece. The timing control circuit 70 in addition to generating theseoutputs has an input 147 which in the preferred embodiment is tied topin No. 7 of the JK flip-flop 116 appearing in FIG. 4. It should beappreciated therefore that the input 147 goes high each time a shallowseam flaw is detected. The shallow seam input serves as aresynchronization signal to center a detected flaw within a workpiecequadrant as defined by the clocking outputs CLK and CLK from the secondfrequency divider. This resynchronization function will be discussed atfurther length after the flaw classification and workpiececlassification circuits have been discussed.

Returning now to FIG. 4, the interaction between the clocking inputsfrom the timing control 70 and the plurality of integrated circuitscomprising the shallow seam channel will be discussed. The shallow seamchannel 110 comprises 2 sixteen bit registers 150, 152 and 2 Quad Andgates 154, 156. A first of the 2 sixteen bit shift registers 150includes an input coupled to the output 117 of the JK flip-flop 116. Ifa shallow seam is detected during the time between clock pulses from thetiming circuit 70 the JK flip-flop changes states and presents a highinput to the first sixteen bit shift register. Since the output 117 fromthe flip-flop is also tied to a first And gate 158 in the Quad And gate154, the input on pin 1 of that And gate 158 is also high. A not clockCLK signal loads this high signal into the shift register 150 and afteran 8 micro-second delay the one shot 120 resets the flip-flop 116.

As the clocking inputs (CLK and CLK) continue a profile of flaw locationabout the workpiece is built up bit by bit in the two shift registers150, 152. Since the clocking rate is four times greater than the speedof workpiece rotation each bit corresponds to one quadrant of workpiececoverage about the workpiece. Since the output from the first sixteenbit shift register 150 is coupled to an input 153 on the second sixteenbit shift register 152, a total of 32 quadrants or 8 revolutions ofworkpiece flaw information is stored in the 2 shift registers.

The two Quad And gates 154, 156 serve to monitor the condition of thebits stored in the 2 sixteen bit shift registers. The Quad And gates154, 156 comprise 8 And gates 158-165. The first And gate 158 has oneinput coupled to the output 117 from the JK flip-flop 116 and a secondinput coupled to the fourth bit in the first sixteen bit shift register150. When both inputs to the first And gate 158 are high, it is anindication that a shallow seam has been detected along the workpiece inthe same quadrant but on two consecutive rotations of the workpiece. Thespeed of rotation and speed of traversal past the probe is such thatthis is an indication that the seam is at least three inches long. Asthe workpiece continues past the probe the detection circuitry continuesto function and flaw indicative information is clocked through the firstsixteen bit shift register until the probe again enters the quadrant inwhich the shallow seam was first sensed. If the same shallow flaw ispresent on the workpiece in the same quadrant the output from the firstAnd gate 158 will be high and the eighth bit in the sixteen bit shiftregister 150 will also contain a high signal. Thus it should be apparentthat input pins 5 and 6 on the second And gate 159 will also be high andtherefore the output at pin 4 from the first quad And gate 154 will behigh indicating that the seam is at least 6 inches long. The processcontinues and it should be appreciated to those skilled in the art thatthe combination of the series coupled sixteen bit shift registers andthe two Quad And gates 154, 156 enable the circuitry to determine thelength of all shallow seams on the workpiece.

The two Quad And gates have eight outputs 170-177 which are coupled toan associated one of eight thyristors 180-187. The eight thyristors arerendered conductive in response to a high output from an associated oneof the And gates inside the two Quad And gate integrated circuits. Aconducting thyristor causes current to pass through an associated one ofeight light emitting diodes 190-197. It should be appreciated thereforethat a first light emitting diode 190 will conduct and therefore emitlight should a shallow seam of greater than 3 inches be detected by theprobe. If the seam length is greater than 6 inches the first two lightemitting diodes 190, 191 will emit light. Since there are eight lightemitting diodes coupled to the eight thyristors, it is possible forthose diodes to provide a visual indication of a seam length of greaterthan 24 inches.

The shallow channel circuit also comprises a multiposition switch 198coupled to the anode of each of the light emitting diodes. When aparticular diode is not conducting its cathode voltage is approximately15 volts. When the LED conducts in response to a turned on thyristor,that voltage drops to approximately 1/2 volt. The multiposition switch198 includes an output 199 which is coupled to one of a plurality ofcontacts on the multiposition switch. In the embodiment illustrated inFIG. 4, the contact is made with the LED cathode indicative of a seamlength of 12 inches or greater. Once the seam length exceeds thisdimension, the output 199 drops from its nonconducting 15 volt value toless than a volt. The output 199 is transmitted to the workpiececlassification circuit 80 (FIG. 6) which categorizes the workpiece understudy.

The deep seam channel in the flaw classification circuit 72 has twoswitches 210, 212 (FIG. 6) similar to a multiposition switch 198 in theshallow seam channel. These two switches 210, 212 allow deep seams inthe workpiece to be classified according to length in a manner identicalto the operation of the switch 198 in the shallow seam channel. A firstof the deep seam switches 210 is labeled a salvage switch in FIG. 6 andtypically contacts an output from LED's in the deep seam channelcorresponding to a relatively short deep seam flaw along the length ofthe workpiece. In FIG. 6, the deep salvage switch 210 has been coupledto the 6 inch deep flaw output. The second of the two switches 212 hasbeen labeled a deep scrap switch and typically is coupled to a LED inthe deep seam channel corresponding to a longer deep seam in theworkpiece. In the embodiment illustrated, the deep seam scrap switch 212has been coupled to the 12 inch LED indicator.

The workpiece classify circuit 80 (FIG. 6) classifies the workpieceaccording to the length and severity of the workpiece seams or defects.The circuit 80 has three inputs 199, 211, 213 from the threemultiposition switches 198, 210, 212. The circuit 80 samples these threeinputs and categorizes the workpiece as either good, salvage, or scrap.As the name indicates, a good workpiece is one that has either nodefects or defects short enough to avoid initiating a change in outputfrom the three multiposition switches 198, 210, 212. Salvage workpiecesare those that have defects but which have no deep defect long enough totrigger an output from the deep scrap switch 212. Scrap workpieces arethose workpieces in which the deep seams or defects are long enough totrigger an output from the deep scrap switch 212.

The workpiece classify circuit 80 includes a plurality of NAND gates216-219 and plurality of Nor gates 220-222 to implement the criteriadescribed. In logic format this circuitry causes the workpiece to beclassified according to the following logic equations:

Good=A·B·C

Salvage=A·C+B·C

Scrap=C

Where A=shallow salvage output, B=deep salvage output and C=deep scrapoutput.

The workpiece classify circuit 80 is coupled to three transistors 224,226, 228. A high input to the base of these three transistors causesthem to conduct current. It should be appreciated to those skilled inthe art that so long as the output from all three switches 198, 210, 212is high, the first of the transistors 224, will conduct and a goodindicator light 230 will indicate the workpiece under examination isgood. In a similar manner, the other two power transistors 226, 288 willbe turned on at an appropriate time when the workpiece is eithersalvageable or scrap. The second transistor 226 corresponds to the scrapindication and the third transistor 228 passes current when theworkpiece is a salvageable piece.

Energization of either of the second two transistors 226, 228 means theworkpiece is not "good" and must be separated from the remainingworkpieces that have passed through the inspection station. To implementthis step, the two transistors 226, 228 are coupled to two relays 232,234. Energization of the first relay 232 by the transistor 226 closes acontact causing a scrap indicator 238 to light. In a similar mannerenergization of the second power transistor 228 energizes a second relay234 thereby energizing a salvage indicator light 240.

Energization of the two relays 232, 234 in addition to energizing thescrap and salvage indicator lights 238, 240 completes an interconnectionto an interconnection panel 244. When the first relay 232 (scrap relay)is energized pins D and E on the panel 244 are connected. When thesecond relay 234 (salvage relay) is energized points C and E areconnected. This panel 244 is in turn coupled to circuitry for routingthe workpiece after it has passed by the inspection station 10 into astorage area for either salvageable, or scrap workpieces. If theworkpiece is good no re-routing procedure is required. Mechanisms andcircuitry for this purpose are known in the art and therefore have notbeen disclosed in the present description. The earlier referenced '809patent to Republic Steel, for example, discloses a mechanism for routingthe workpieces in response to control signals from the routing circuit80.

Once the workpiece has left the inspection station it is necessary thatthe thyristors 180-187 be turned off so that subsequent workpieces maybe analyzed and classified. It should be appreciated that in addition tothe thyristors 180-187 comprising a portion of the shallow seam channel,there are a plurality of thyristors in the deep seam channel which arealso reset once the workpiece has exited from the inspection station. Asthe workpiece exits the inspection station a switch (not shown) coupledto contact pins A and B on interconnection panel 244 is closed therebyenergizing a relay 246 shown at the bottom of FIG. 6. Energization ofthis relay 246 closes one associated contact 248 and opens a secondassociated contact 250. Closure of the first contact 248 causes a 500millisecond output from a one shot 252 which in turn causes a 50millisecond output from a second one shot 254. The second one shot turnson a transistor 256 which has its emitter coupled to the anodes of eachof the light emitting diodes 190-197 via an interconnection 255. Whenthe transistor 256 conducts these anodes receive a low voltage inputthereby turning off the LED's. This effectively resets the thyristor/LEDpair and enables the shallow seam channel to be reset to analyzesubsequent workpieces at the workpiece station. It should be appreciatedthat although not shown a similar interconnection exists for resettingcorresponding LED's and thyristors in the deep seam analysis channel.The opening of the second contact 250 disables the routing mechanism(not shown) by opening the path to pin E from either pin C or pin D onthe interconnection panel 244.

As the defect classifying circuitry 72 is classifying each flaw detectedby the probe the timing control circuit 70 is also controlling theoperation of a marker delay circuit 74 (see FIG. 7). Since the exemplaryinspection technique uses four probes and four markers there are fourmarker delay circuits identical to the marker delay circuit 74 shown inFIG. 7. The marker delay circuit 74 has three inputs 144, 260, 76a. Oneof the inputs 76a is coupled to one of the four shallow seam inputs.Whenever this input 76a goes high in response to the detection by theprobe of either a shallow or a deep seam the input 76a causes a changein state of a flip-flop 266 in the marker control circuit 74. Thischange in state is stored within the flip-flop 266 until that flip-flopreceives a "high" signal on a second input 260. Both this second input260 and the third input 144 to a programmable shift register 146 comefrom the timing control circuit 70. The input 144 is coupled to thefirst frequency divider 132 and therefore comprises an oscillatingsignal with a frequency 64 times greater than the frequency of rotationof the workpiece. The second input 260 is also coupled to this firstfrequency divider but has been delayed by approximately 2 microsecondsby the one shot 142 (FIG. 5).

The sequence of entering signals into the programmable shift register146 from the probe is as follows. A defect is detected and a shallow ordeep seam input appears at the flip-flop 266. This input causes theflip-flop to change states indicating that a defect has been detected.The next signal on the input 144 from the first frequency divider 132causes a high bit to be stored in the first bit of the programmableshift register 146. The output from the first frequency divider 132 isalso transmitted through the 2 microsecond one shot 142 and input to theflip-flop 266. This causes the flip-flop to again change states andawait the receipt of subsequently detected flaws. As the first frequencydivider generates output signals to the input 144 the defect informationstored in the programmable shift register 146 is clocked through theshift register to an output 270.

The programmable shift register introduces a requisite timing delaybetween the receipt of a defect signal and the activation of the marker14. The correct delay time is a function of the mechanism used to markthe defect and can vary from one system to the next. The programmableshift register 146 is a 64 bit register and therefore the maximum delaycorresponds to one workpiece revolution. Since the marker mechanismtakes a finite time period to bring the marker 14 in contact with theworkpiece 18, however, the actual delay typically is somewhat less thanthe time required for one workpiece rotation. The programmable shiftregister 146 is coupled to a delay selector switch 272 by a series ofsix inputs. By properly programming the delay selector switch 272, it ispossible to introduce a delay of anywhere from 1 to 64 clock pulsesbetween the introduction of a "high" defect signal at pin 7 of the shiftregister 146 to the output of that "high" signal on pin 10.

The appearance of a high output from the programmable shift register 146at the output 270 causes a one shot 280 to turn on a transistor 282. Theturned on transistor energizes a relay 284 in the delay circuit which inturn closes two contacts 285, 286. Closure of these contacts 285, 286causes marker actuation circuitry (not shown) to cause the marker 14 tocome in contact with the workpiece 18 at a location approximatelycoincident with the position of the detected flaw. As noted above, theapplication of a mark to the workpiece occurs at a position downstreamof the probe 12 and in the preferred embodiment of the invention themark is applied one rotation of the workpiece subsequent to thedetection of a particular flaw.

As mentioned above, detection of a flaw on the workpiece causes thetiming circuit 70 to resynchronize itself and thereby center that flawwithin a workpiece quadrant. This function is performed by theintroduction of an input 147 to the second frequency divider 134 eachtime pin 7 on the flip-flop 116 receives an input. Receipt of a shallowor deep seam flaw causes the signal at this pin to go high and changesthe state of a one shot 288 causing the one shot to generate a highoutput 289 to the second frequency divider 134.

The second frequency divider 134 which generates the clock (CLK) and notclock (CLK) signals comprises a programmable divide by N four bitcounter which has been programmed to divide by 16. Receipt of the highinput 289 from the one shot 288 resets the second divider 134 to a countof eight. Resetting the count to 8 centers the sensed flaw within theworkpiece quadrant in which it has been detected. As the clocking pulses143 from the first divider 132 continue, the second frequency divider134 counts down to 0 and then outputs a clock pulse (CLK) so that theclock signal CLK appears 8 counts or one eight bar rotation afterreceipt of the sensed flaw.

By resynchronizing the timing function used to clock the deep andshallow channel shift registers the accuracy of flaw lengthdetermination is maintained even though the drive roller 16 used torotate the workpiece past the probe may vary slightly in its operation.It is possible, for example, that even though the thumbwheel switcheshave been properly adjusted for the particular diameter bar the roller16 may slip and thereby produce a slight missynchronization between thetiming circuit 70 and the speed of rotation of the workpiece. Such amissynchronization is corrected for each time a defect is detected bythe resynchronization input 147 to the second frequency divider.

A second divide by N counter 290 is coupled to the synchronization oneshot 288 and resets that one shot after one complete bar revolution. Ahigh output 289 from the one shot 288 sets this programmed counter 290to a count of four. Since the counter 290 is coupled to the clock (CLK)output from the second divider 134 the counter 290 changes counts onceevery quarter of bar rotation. When the counter 290 counts down to zeroits output 291 goes high resetting the one shot 288 thereby enabling itfor resynchronization of the clock (CLK) pulses on subsequent barrevolutions past the probes.

While the preferred embodiment of the invention has been described witha degree of particularity it should be appreciated that certainmodifications can be made. For example, rather than 64 clock pulses perworkpiece revolution it is possible that some other standard frequencycould be adopted and adjustments made in the digital circuitry tocompensate for such adjustment. Rather than four quadrants the workpiececould be conveniently divided into some other integer number of segmentsto more accurately scan for flaws and defects. An exemplary techniquefor rotating the workpiece has been illustrated in FIGS. 1 and 2 andother mechanisms are known in the art for scanning probes in relation torotating workpieces. The present circuitry would function equally wellshould the probe be rotated and translated past a stationary workpiecealong a helical path. The technique for classifying the workpiece isalso subject to change. The criteria for determining a "good","salvageable", and "scrap" workpiece might be altered and indeed will bealtered as the performance criteria of the bar is changed. From theabove it should be apparent that certain modification could be made inthe scanning of workpieces without departing from the spirit or scope ofthe invention as defined in the appended claims.

I claim:
 1. Apparatus for examining workpieces and categorizing themaccording to defect severity comprising:(a) defect detector means forsensing defects in a workpiece as said workpiece and detector means moverelatively past and rotationally with respect to each other and havingan output for transmitting a defect signal in response to the detectionof a defect; (b) defect classifying means having an input for receivingdefect signals for classifying the workpiece according to defectseverity as indicated by said defect signals; (c) a single timing meansfor generating timing signals and including outputs to said defectclassifying means, said single timing means dividing a revolutionbetween said defect detecting means and said workpiece into a number ofinspection segments; and (d) synchronization means for synchronizingsaid inspection segments when a defect is sensed to locate such defectapproximately in the center of an inspection segment.
 2. The apparatusof claim 1 wherein the defect classifying means comprises:(a) serialstorage means for storing defect signals from the detector means; and(b) gate means for determining the length of a defect along theworkpiece from the position of the defect signals in said storage means.3. The apparatus of claim 2 wherein the timing means generates anadjustable number of signals to the storage means per revolution betweensaid workpiece and said defect detecting means to clock the defectsignals through the storage means at a rate related to the speed ofrotation.
 4. The apparatus of claim 3 further comprising a marking meansfor receiving defect signals and marking the position of defects on saidworkpiece in response to the receipt of said defect signals, saidmarking means includes a delay storage means coupled between a defectsignal input and a marker energization means and the timing means clocksdefect signals through said delay storage means at a rate equal to amultiple of the frequency of the signals clocking the serial storagemeans to delay marking a defect until the workpiece has rotated thatdefect at least one revolution after detection by the detector means. 5.A method for classifying workpiece defects according to defect lengthcomprising the steps of:(a) rotating and translating a workpiece past aprobe which indicates the presence of a defect by producing a signaloutput; (b) generating a series of pulses with a repetition frequency aninteger multiple of the frequency of rotation of said workpiece, saidworkpiece thus being divided into an integer number of inspectionsegments; (c) storing signal outputs from said probe in a serial storagemeans; (d) coupling the storage means to the series of pulses to clockthe output through the storage means at a rate equal to the repetitionfrequencing; (e) sensing the condition of said storage means tocorrelate said condition to the length of a sensed defect; and (f)resynchronizing the clocking of said storage means when a defect issensed to position said defect approximately in the center of a segment.6. The method of claim 5 wherein the repetition frequency is four timesthe frequency of rotation to allow the workpiece to be divided into fourquandrants.
 7. A method of workpiece flaw detection comprising the stepsof:(a) rotating and translating a workpiece past a probe, said probeincluding an output for generating defect signals corresponding to thepresence of flaws in the workpiece; (b) coupling the defect signals to asequential storage register which includes an input for receiving aclocking signal to clock such defect signals stored in the registerthrough said register; (c) generating repetitive clocking signals with afrequency at least twice the frequency of rotation of the workpiece thusdividing each rotation into at least two segments; (d) sensing the stateof the register to determine the length of a detected flaw; and (e)resynchronizing the clocking signal upon detection of a flaw on eachworkpiece revolution to position the flaw approximately in the center ofa segment.
 8. Apparatus for detecting and categorizing flaws in aworkpiece comprising:(a) means for rotating and translating a workpiecepast a probe, said probe including an output for transmitting defectsignals corresponding to the presence of flaws in a workpiece; (b) meansfor storing defect signals as they are generated by the probe includinga serial storage register with a clocking input, the storage means alsoincluding a signal generator for clocking the storage register at a rateequal to a multiple of the frequency of rotation of a workpiece todivide the profile into segments of workpiece circumference; (c) meansfor resynchronizing said clocking of the storage register to locate adetected defect approximately in the center of a segment; and (d)sampling means for sampling the state of the means for storing defectsignals; said state representing a profile of workpiece condition over arange of workpiece surface and indicative of the length of a detectedflaw.
 9. A method of inspecting a workpiece for defects comprising thesteps of:(a) causing relative linear and rotational motion between aworkpiece and a test probe, said test probe detecting the presence of adefect and producing a signal indicative thereof; (b) dividing arevolution of relative rotation into a number of inspection segments;and (c) synchronizing said inspection segments when a first defect issensed to locate such defect approximately in the center of a segment,such segment defining a capture segment.
 10. The method of claim 9further including the step of:(d) disabling resynchronizing of saidinspection segments after a first defect is sensed and until the capturesegment is encountered on the next revolution of relative rotation. 11.An apparatus for inspecting a workpiece for defects comprising:(a) atest probe for sensing the presence of defects and producing signalseach indicative of a sensed defect; (b) moving means for causingrelative linear and rotational motion between a workpiece and the testprobe; (c) clock means for generating a series of pulses, the number ofpulses being an integer number per revolution of relative rotation, saidpulses dividing a revolution into an integer number of segments; and (d)resynchronizing means for resynchronizing said pulses of said clockmeans to locate a detected defect approximately in the center of asegment, such segment defining a capture segment.
 12. The apparatus ofclaim 11 further including disabling means for disabling furtherresynchronization of said pulses of said clock means after a firstdefect is sensed and until the capture segment is encountered on thenext revolution of relative rotation.